U.S. Pat. No. 4,725,857 discloses a compact printer having a unique integral sheet feeding system that is interchangably operative with a continuous, edge perforated tractor media feeding system. Both feeding systems share a feeder-platen member which moves the media from a region near the bottom of the printer housing through the print zone and out through the top of the housing. Sheet feed is effected by providing cyclic feed contacts between the top sheet of a supply station stack and a friction surface(s) on the feeder-platen. To switch to the tractor media mode, a control lever is moved to disengage the sheet supply from the feeder-platen and to open the passage for tractor media to be fed above the sheet media stack, into the printing region, where it can be positioned on pins on the ends of the feeder-platen that cooperate with the perforations of the tractor media.
In certain printer embodiments, the provision of the tractor media pins on the feeder-platen presents difficulties. For example, when using a plurality of different color print heads that each traverse entire line portions of the print media; the protruding pins on the feeder-platen can block the passage of "end" print heads, which is necessary to allow "central" print heads to cover the full scan line distance. This problem can be solved by retractable pins or pivoting print heads, but those solutions are not desirable because of their mechanical complexities.